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Chapter 7 TITANIUM MELTING, ALLOYING, MILL PROCESSING, AND HEAT TREATING The conversion of raw titanium metal sponge to a consolidated f o rm useful for structural purposes involves several processing steps. The slam of these steps incorporates much metallurgical knowledge, perhaps even more than that required to make sponge. Although only a f ew U . S. . companies are involved in producing sponge, more than a score of companies are sponge melters and mill product fabricators. This chapter present s brief reviews and comments on the technologies involved in melts ng, alloying, mill processing, and heat treating . Ingo Sac Melting The principal product associated with the melting of titanium sponge is ingot. The process of melting titanium also is used to make castings and spherical powder and, more recently, to produce bulk metal from lightweight forms of scrap (e.g., turnings and grindings). Pre se nt Prac Lice Titanium ingot is the precursor form for most titanium mill products (the exceptions are the as-cast preforms and the preforms produced by powder metallurgy techniques). The steps required to make ingot include: 1. Formulating the composition--designing the alloy chemistry and determining the required portions and forms of alloy constituents (sponge, scrap, alloy additions ~ . 2. Preparing charges and electrode--weighing unit charges ~ sponge, scrap , alloy additions), pressing blocks f rom each unit charge , assembling blocks into elec bode shape (weld ), and allowing f or and adding bulk scrap to electrodes if bulk scrap is a c oust i tuent (weld ~ . Positioning consumable electrodes in vacuum arc furnaces for initial melting and locking up, evacuating, and backf illing furnace with inert gas at partial pressure. (Evacuating and backfilling is repeated as necessary to secure acceptable contamination-free conditions). 63

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64 Performing first-melt operations--converting consumable electrode to f irst-melt ingot . Performing second-melt operation using first melt ingot as consumable electrode f or second melt ing . For tr~ple~elted ingots, repeating step 5 . 7. Reducing power gradually toward conclusion of second- or third-melt operations to minimize pipe--the hot topping procedure. Removing ingot from furnace mold and inspecting it for defects and conditioning the surf aces as required . A schematic diagram of the f eatures of the ingot melting procedure is shown in Figure 9. The factors affecting ingot quality and, subsequently, the quality of the ultimate mill product, as determined by ingot-preparation steps, are listed in Table 7; Ti-6Al-4V alloy is used for illustrative purposes. All (1981) U.S. titanium sponge producers melt ingot and at least six additional companies purchase sponge and scrap titanium for converting these raw materials to ingot. These companies use similar equipment but it may vary in detail so that each company's overall process may be somewhat different from that of the others. Nevertheless, most companies apparently melt ingots to the same rigorous specif ications because the end products from different melters are markedly similar. Most of the titanium ingots produced in the United States weigh about 9, 000 lbs and are approximately 30 inches in diameter. S ome smaller (e.g., 6,000-lbs ingot 23 i nches in diameter) and larger (e.g., 22, OOO-lbs ingot 39 inches in diameter ~ are made . The ingot s produced are ei ther double~elted or triple~elted . Ingot melting is a sophisticated, time-consuming operation, and it is quite possible that this process is one of the bottlenecks in the production of titanium products. The panel concluded that there appears to be insuf f icient ingot melting capacity in terms of accommodating surges in demand (e . g., those experienced in 1979-1980~. The Future of Titanium Melting The consumable electrode, vacuum arc remelting (VAR) process has proven to be an excellent method for consolidating titanium sponge, mixed with scrap and alloying additions as appropriate, in sizes up to 39 inches in diameter and up to 22,000 lbs. The solidification pattern in consumable electrode ingots minimizes alloy segregation. Available basic technology for producing titanium ingots appears adequate for the near future.

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65 I 4 it', Store Compact T' Alloy Weigh Initial Melting ,'1 -'. :~, )1 ~ , Titanium consumable l ~ Water outlet ~ Compact assembly press (Weld ~ Liquid-metal pool Sol Edified metal r electrode _ Arc _ iVater-cooled _ copper crucible ] _ ._Wa~er r - inlet | ~Water ~- Ingot outlet conditioning Water-cooled copper crucible _m - 3 <~ Stub Weld Second Malting Log Am, Ingot conditioning Titanium consumable electrode (ingot from initial melting} l - 6 Water inlet Figure 9 Flow diagram for the production of double-melted titanium ingots using consumable electrode methods. Triple-melted ingots are made similarly.

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66 TABLE 7 Factors Af fecting Ti-6Al-4V Ingot Quality and Ultimate Product Capabilities Ca tegori es Composition formulation Principal elements (Al and V) Int ers t i tial element s ~ principally O) Impurity elements (e.g., Fe , Cu. Si) Intentional ocher elements (e .g . Y2O Raw materials selection Sponge titanium Alloying additions A1-V master alloy Other make-up (Al, TiO Scrap Raw materials preparation Component weigh up Constituent blending Blend storage Consumable electrode preparation Charge consolidation (block press) ng) Weld assembly of blocks and holding stub Reme 1 t e lec bode ~ f ram ingot ~ Preconditioning and weld to stub Ing at mel tiny Furnace type employed Number of times melted Power input schedules St eady-s Late aberrations Hot topping anomalie s Me It chamber pressure aberrations Vo let lies Air inleakage Pin-hole water leaks and crucible burn-through Ingot s ize Ingot conditioning and testing Surf ace conditioning Pipe identif ication and treatment Metal characterization: chemical met allographic Possible Variants Low side, mid-range, high side Low side, mid-range, high side Low cant ent, maximum c ant ent Trace to large quantity Purity (bulk, volatilesa, inclusion Purity ~ bulk and inclusions Purity Compos it ion ~ known t o unknown) Purity (bulk and inclusions) Form (small to large piece sib Ratio (O to 100 percent of charge) Accuracy Mixing compatibi lity ~ segregation b size, shape, or density) Contamination Strength, contamination Contami net i on Orientation (heterogeneity) Contamination Consumable, non-consumables Double melted, triple melted) Unf used seams Large and/or open pipe Loss of arc (melt interrupt) ons) Contamination Contamination Homogeneity and pipe control Contamination (removal of) Ingot yielde, possible f laws in center of ingot Composition anomalies Structural anomalies a High volatile content can result in melting difficulties b Form influences utilization mode--incorporation in blended batches or as weld-on attachments to electrode assembly. c Possible elimination of high-density inclusions d pa ssible elimination of low-density inclusions e Yield low if pipe section cannot be used.

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67 Some evolutionary ingot melting developments that might improve the titanium availability situation are described as follows: 1. Nonintegrated melters generally cannot readily melt the . acid-leached sponge produced by the domestic sponge producers. This i s due to the high volatiles content of the sponge and to the lack of adequate furnace vacuum pumping capacity by the nonintegrated melters. Demonstration is needed to show what modif ications must be made to the pumping equipment of furnaces currently suitable only for the melting of vacuum-distilled sponge so that they can adequately melt acid-leached sponge. 2. There are currently in operation on a small scale, furnaces (inert-electrode vacuum arc, electron beam, and at least one plasma arc remelt) capable of converting various forms of scrap titanium to more useful forms in skull-melting type operations. Demonstration is needed of the modifications required to i mprove the produc t ion rate s of such f urnaces . 3 . A need is fore seen f or ingots larger than can be produced in currently available titanium vacuum arc melting furnaces. These are for applications in the areas of ship and hull structures and electric-generating utility plant equipment (e.g., surface condenser tube sheets and generator retaining rings). Demonstration is needed of modif ications to currently available large (up to 60 inches in diameter) VAR furnaces (now set-up for s teel melting ~ so that they can be suitable f or melting titanium. Co nstruct ion of larger vacuum arc f urnaces specifically for the melting of titanium ingots of up to 50 inches in diameter is an alternative path. Subsequently, the production of ingots of 30, 000 to 40, 000 lbs needs to be demonstrated . ~ The panel has been made aware that two of the U . S . producers are installing new f urnaces capable of melting 40,000-lbs ingots.) 4. Re ctangular slabs for plate rolling currently are produced from round ingots by press forging. Ingots having a rectangular section would be preferable as precursor slab for plate production. Demonstration of melting methods to produce rectangular-section ingots is needed (e.g., the electroslag remelting methods employed by the Soviet Union in producing a square-section ingot, one of which was exhibited at the 1981 Paris Air Show). 5. Highly alloyed or otherwise difficult to melt ingots and their mill products have experienced relatively small demand. However, they have an important position in the application of titanium; producers meet this small demand with various forms and degrees of reluctance.

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68 Alloying Several thousand t itanium alloys have been examined on a research and development basi s . From this extensive activity, more than a hundred compositions have been produced commercially over the past three decades of titanium production. Some old alloys have disappeared from the popular) ty listings and new alloys have been added. In the United States, the active list of currently available commercial alloys numbers around 20. A number of important compositions to be considered f or thi s discussion are listed in Table 8. The Ti-6Al-4V alloy in this ~ isting has been the most used alloy (about 50 percent ~ over a several-year per' ad (see Chapter 8) . Unalloyed titanium is the next most popular material (currently about 30 percent usage). All other alloys therefore share the balance of usage (about 20 percent ~ . TABLE 8 Titanium Alloys of Current General Interest Offered by Producers in the Uni ted States Nominal Compositions, Weight Pe rcent Common Name 'Type Unalloyed Ti, 99.2a Commercially Pure Alpha Ti-O. 15 ~ o O .20 Ed Pd alloy Alpha Ti-O .3 Mo-O .8 Ni Ti-cod~ 12 Alpha Ti-SAl-2 . 5Snt A-llO Alpha Ti-6Al-2 Cb-lTa-O . 8Mo 6-2-1-1 Nea r-alpha Ti-8Al-lMo-lV 8-1-1 Near-alpha Ti-8Mn 8 Mn Alpha-beta Ti-3Al-2 . 5V Half 6-4 (or 3-2 1/2) Alpha-beta Ti-4. 5Al-5Mo-1. 5Cr Corona 5 Alpha-beta Ti-5Al-2Sn-2Zr-4~10-4Cr Ti-17 Alpha-beta Ti-6Al-4~5 6-4 Aipha-be ta Ti-6Al-6V-2Sn 6-6-2 Alpha-be ta Ti-6Al-2Sn-4Zr-2MoC 6-2-4-2 Alpha-beta Ti-6Al-2Sn-4Zr-6Mo 6-2-4-6 Alpha-beta Ti-7Al-4Mo 7-4 Al pha-heta Ti-3Al-8V-6Cr-4Mo-4Zr 38-6-44 (Beta c) Beta Ti-3Al-13V-llCr 13-11-3 ~ or Beta I ~Beta Ti-3Al-lOV-2Fe 10-2-3 Beta Ti-3Al-15V-3Cr-3Sn 15-3-3 (or 15-3 ~Beta Ti-4 . 5Sn-6Zr-ll . SMo Beta III Beta a Several grades of CP Ti are produced that dif f er in impure ty level . b High-puri ty grades of these alloys are available and are designated wi th the suf f ix ELI, meaning extra low interstitials . c A silicon-containing grade also is available.

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69 Emerging Alloys Titanium alloys are classified as alpha, beta, or mixed alpha-beta depending on the metallurgical stability of their crystal phases at room temperature. Unalloyed grades and the Ti-5Al-2.5Sn alloy are of the alpha type . This type cannot be heat-treated to increase strength but i s noted f or its excellent weldability. In addition to Ti-6A1-4V, the Ti-6Al-2Sn-4Zr-6Mo, Ti-6A1-6V-2Sn, Ti-4. SA1 -SMo-1. 5Cr, Ti-5Al-2Sn-2Zr-4Mo-5Cr, and Ti-8A1-lMo-lV alloys are alpha-beta compositions. The Ti-lSV-3Cr-3Sn-3Al, Ti-13V-llCr-3A1 and Ti-3Al-8V-6Cr-4Mo-4Zr alloys are representative of the beta alloy category. Figure 10 is a schematic representation of the relationships among alloy chemistry, microstructure, and alloy characteristics arranged according to the a~loy-type classification scheme. Several compositions are of particular interest because they are considered to be newly emerging materials that are expected to play important roles in the future application of titanium. These are: 1. Ti-O.3Mo-0.8Ni, 2. Ti-4.5Al-5Mo-1.5Cr, 3. Ti-5Al-2Sn-2Zr-4Mo-4Cr, 4. Ti-3Al-lOV-2Fe, and 5. Ti-3Al-15V-3Cr-3Sn. The Ti-0.3Mo-0.8Ni alloy is expected to be used in industrial applications for corrosion resistance. The crevice-corrosion resistance of this material is much better than that of unalloyed titanium and it is almost as good as that of Ti-0.2Pd alloy, but the material is not as expensive. The Ti-4.5Al-SMo-1.5Cr alloy was developed for its high fracture toughness at moderately high strength levels. This material also is hardenable by heat treatment to greater thicknesses than other commonly available alpha-beta alloys. Thus, it is expected that this material will be used in increasing quantities in forging applications where high strength in thick sections is a requirement. The Ti-5Al-2Sn-2Zr-4Mo-4Cr alloy was developed by General Electric's Gas Turbine Engine Division engineers and is being promoted for use in engine compressor discs because of its excellent combination of propert ie s . This too is an alpha-beta type alloy with high toughnes s, good depth of hardenability, and improved strength at elevated temperatures . The Ti-3Al-lOV-2Fe alloy i s a nea ~ beta type alloy t hat i s easier to f orge at lower temperatures than, for example , the Ti-6A1-4V alloy, and it can be hardened deeper to higher strength level s. This material is a prime candidate for the isothermal forging process. It has good toughness and ductility over a wide range of strengths and currently is being used in a number of applications in new aircraf t under development .

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Alph~Stabilizing Elements For example: Aluminum Oxygen Nitrogen 70 Eleta~sabilizing Elements for example: Molybdenum Iron Vanadium Chromium Manganese Increasing Quantities of Alpha Stabilizers Promote Alpha Phase ~ncreasing Quantitics of Bem Stabiliz~s Promote Bem Phase l Alpha Mi ed Near Stru ur Alpaha Alpha-8e B a S u ur | | (some beta) | Structure | (some alpha) | | Unalloyed T;- Ti- Ti- Ti- Ti- Ti- Ti- T;- Ti- Ti- Ti Ti 5AI- 5A1 8Al- 6AI- 6AI- 6AI- 6AI- 8Mn 8Mo 11 .5Mo- 1 3V 2.5Sn 6Sn- 1 Mo- 25n 4V 6V 25;n- 8V- 6Zr- 1 1 Cr 2Zr 1V 4Zr 2Sn 4Zr- 2Fe 4.5Sn 3AI lMo- 2Nto 6Mo 3AI 0.2si H;gher density Increasing heat tr~atment response- Higher stort-time strength -Highet creep strengtt Incrcasing snain rate xnsitivity _ ~--- Improved weldabili~'r e ~ ~_. ~ ~._ ~ - _.~_ ~_' ~w_~e-~ Figure iO Sc~hematic relatianships: titaniun alloying effec s on structure and selected ~1tcy charac~ristics.

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71 The Ti-15V-3Cr-3Sn-3A1 ( 15-3 alloy) is a beta alloy that was developed for ease of strip producibility and cold fabr~cability. It Is f oreseen that hand-mill sheet may be largely replaced by continuously rolled strip because strip is potentially a less expensive product. In addition, secondary forming operations might be accomplished at room temperature with the 15-3 alloy, and this would lead to still additional cost savings in fabricating parts. In its strip-rolled and formed condition, this material can be heat-treated to a wide range of strength level s . In addition to these titanium compositions, a special class of alloys known collectively as titanium aluminides is under development. The interest in the aluminides stems from their excellent high-temperature streng ths, which are comparable to those of nickel-base superalloys but the aluminides have lower density. Problems with developmental compositions under study have been their poor hot fabricability and low ductility at ambient temperatures. There are two subclasses of titanium aluminizes: those with a Ti3A1 base and those with a Ti-A1 base. Currently, the former shows more promise than the latter. Both types noted f or higher modulus values than conventional titanium alloys and their oxidation re si stance is generally good although coatings may be required for gas turbine applications. Compositions and processing methods f or optimizing parts production and properties are under development . The Future of TO tanium Alloying There appears to be an adequate family of titanium alloys to handle all cur rent applications . The mainstay alloy will remain Ti-6Al-4V for the near future. The possibilities are great for the extensive use emerging beta alloys T~-lOV-2Fe-3A1 and Ti-15V-3Cr-3Sn-3A1 materials promise an economy in production and application _ _ with other currently available compositions for specific uses. Of the since these not achievable After further development, it is expected that the optimized compositions from the family of titanium aluminides currently being explored will find relatively small use, perhaps up to a million lbs of product annually, in high-pressure compressor and lower-pressure turbine stages of gas turbine engines. Demonstration of the need for the special attributes of the aluminide type alloy might hasten development. Little need is seen for intensive alloy development because of complications that accrue in scrap recycling due to a proliferation of grades to be identified, sorted, and subsequently factored into the plans for recycling the scrap. In this respect, a small but versatile family of titanium alloys contributes to a healthy industry. On the other hand, the matter of improved use of scrap titanium might be addressed by an alloy development program. Such a program was conducted by titanium specialists in the Soviet Union who developed an

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72 entire line of alloys derived from various sources of titanium scrap (Gurevich et al. 1973~. Demonstration of pref erred alloy types and specific compositions that could be generated from various scrap is desirable. The growing importance of precision-cast and of powder-metallurgy- molded titanium shapes may well prompt the development of alloys that possess special combinations of properties but that are not feasible using conventional ingot metallurgy. Mill Processing Ingots of titanium and titanium alloys are fabricated in high-temperature, metal-working operations to produce mill products. Considerable technology is involved in simultaneously producing the desired mill product shape and dimensions and imparting the preferred metallurgical crystal structure so as to obtain optimum properties. Control of temperature, time at temperature, degree of def ormat ion, and cooling rate are the most important variables that the mills can ad just to achieve the preferred structure and properties in end items. The contamination of the work piece during fabrication is to be minimized during the operations and to be eliminated by conditioning the work piece after fabrication. Typical Current Practice The common mill product fabrication sequence starts with the break-down forging of an ingot to a bloom. Break-down forging i s accomplished at high temperatures (e.g., 1150C) and the finished billet commonly is in the form of either circular section (e.g., rounds for billet, bar, and extrusions) or rectangular section (e.g., slabs for flat rolling) products. Octagonal- and round-cornered-square-section billets also are produced. Billets may be used directly by the forge shops to make forged shapes. The initial forging operation to produce billet shapes commonly is followed by a surf ace conditioning operas ion (grinding) to remove surface contamination, laps, tears, and cracks re suiting f ram def ormation abnormalities . Considerable loss of metal occurs because of the necessity to condition billets. Conditioned round billets from the initial forging operation also may be fabricated in rotary forging machines (e. g., in GEM machines ~ or in rolling mills to produce small-section-size billets and bars. Bars and coils of rod may be conditioned to remove contamination and used in thi s form or they may be sent to wire producers for further fabrication. Some billet s are cut to precise shaped blanks as precursor feed to extrusion pre sses . As might be expected, a wide variety of extruded shapes and seamless tubing can be produced from round-sect' on extrusion billet. * Gesellschaf t fur Maschinenbau-und-fertigungstechnik.

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Slabs from the initial forging operation usually are rolled after conditioning to make plate, sheet, strip, and some foil. Plate rolling commonly is accomplished on a toll basis at one of the steel mills. Ro lied plates may be returned to the primary titanium producer f or flattening, surface conditioning, and shape cutting operations . Plates for further conversion to sheet may be conditioned, cut to unit lengths, stacked (four or more), and enclosed in a steel envelope. These packs are then pack-rolled to produce the so-called hand-mill shee t product . Sheets may be surface-ground and pickled to achieve f inal dimensions and surface condition. Slabs for conversion to strip may be rolled to a hot-band coil, treated at this stage to enhance their metallurgical characteristics (e. g., by annealing) and surface condition (e.g., by pickling), and subsequently re-ro~led to strip dimensions. The final stages of stri~rolling may be cold-rolling operations. Annealing and surface condition) ng operations commonly are used as the f inal steps in producing strip. In a notable advance, one U.S. producer successfully operates a continuous, inert-gas-annealing strip furnace. Strip may be used directly as flat-rolled product or as precursor material for foil. The most important use of strip currently is for the production of rolled and welded tubing. Coils of strip are slit to the proper width and then rolled up and seam-welded in continuously operating tube lines. Much more rolled and welded tubing (in unalloyed titanium grades) is used than seamless tubing produced by extrusion. The Future of Mill Processing Fabrication schedules have been worked out that result in optimized characteristics for each titanium material and, in many cases, there are several schedules that can be followed to produce different characteristics in a given material. For example, the Ti-6Al-4V alloy may be fabricated using either an alpha-beta or a beta schedule. Further, different mills might use slightly different schedules to produce a product with very similar characteristics. There is considerable flexibility in the matter of achieving preferred material characteristics via fabrication scheduling. At the same time, this has led to the existence of a variety of microstructures in products for the same or similar applications. Some observers of the industry believe that primary fabrication schedules have yet to be optimized to produce optimum properties for titanium alloys and to produce consistency or uniformity in material characteristics. Some evolutionary developments in this area that can be foreseen involve the following: 1. Most mill products are produced with relatively coarse microstructure and indefinite amounts of residual cold work. The term "coarse microstructure" is used with respect to the

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76 is to ache eve metallurgical stabilization of the acicular structure. Typical heat treatment exposures for beta annealing are 1/2 hour at 1040 C terminated by either water quenching or air cooling to room temperature, followed by reheating from 700 to 730F, holding for 2 hours, and terminating by air cooling. Strengthening Heat Treatments Heat-treatable titanium alloys, such as the Ti-6Al-4V alloy, can be heat treated to a high-strength condition in a two-stage thermal exposure consisting of a solution heat treatment and an aging heat treatment: 1. Solution heat treatments. Solution heat treatments are designed to develop a preferred microstructure that may also be amenable to age hardening during a subsequent heat treatment. The effectiveness of certain solution heat treatments may be dependent upon the exposure temperature and the cooling rate. Quick cooling is mandatory and a minimum quench delay time and rapid cooling rates are preferred. Although titanium materials are not ordinarily used in the solution-treated condition, material in this condition may be characterized by having relatively low strength and high ductility. 2. A ins heat treae~encs. The second stage of the treatment is imposed on the solution heat treated material. Aging treatments in the 370 to 590C temperature range may be used although temperatures in the 480 to 610C range are the most common. Exposure is commonly for 2 to 8 hours and is terminated by air cooling. The solution-treated material is metallurgically modified during aging treatments by precipitation and transf ormation reactions. Aged materials can have a very high strength in combination witch a moderately low bu~ usable ductility . 3. Overaging heat treatments. Treatments of this kind may be superimposed on solution-heat-treated material or on solution-treated-plus-aged material. Overaging treatments merely cause the further progression of the metallurgical reactions that occur during aging. The net result is that peak hardness is surpassed leading to a sof teeing of the material and increased ductility as compared to the aged condit' on. Thermal exposures in the 590 to 650C range, usually for about 4 hours, can be used for averaging. The treatments are terminated by air cooling. The Future of Heat Treating The heat-treatment response of titanium alloys is relatively modest and no breakthroughs are expected. However, approaches for product improvement through heat-treatment techniques are promising.

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77 The mill-annealed heat treatment, which is used extensively, is a form of stress-relieving treatment that often leaves a considerable amount of internal strain In the material. A better final heat treatment involves annealing at temperatures that produce low temperature equilibration; this stabilizes the alloy against further transformation during elevated temperature service. Such annealing treatments also accomplish stress relief. Stress-relieving treatments below recrystallization temperatures are useful in reducing internal stresses from welding, machining, or forming operations. The most essential prerequisite to good properties in the solution-treated-and-aged condition is an initial fine grain size produced by proper mill processing to the semifinished form. In this condition, good combinations of properties are obtained after aging heat treatments that result in the precipitation of fine alpha and fine alpha-sub-two (Ti3Al) phases. Little hope is seen of utilizing the coherent omega phase as a strengthening mechanism. Martensitic transformation does not give a strongly hardened transition phase as it does with steels; thus, there is little hope in exploiting the martensitic reaction for property improvement. However, beta quenching of alpha-beta alloys to form martensite is extremely useful as a grain refining technique. The martens~tic structures thus produced can be annealed to form lamellar structures or reworked in the alpha-beta f ield and recrystallized by heat treatment to form equiaxed-lamellar structures. Specifications for Titanium-Base Ingots, Mill Products, and Alloying Additions Ingot No public specifications are issued exclusively for the control of titanium ingots of either unalloyed or alloy grades. However, AMS 2380 includes the technical requirements for the preparation of ingots. Ingots for quality products are manufactured in two widely recognized quality categories--standard quality and premium quality. Although these quality measures generally apply to the mill product resulting from ingot fabrication, (e.g., bloom, billet, bar, plate, and sheet), the ingot starting material must, of course, have an equivalent quality. Subcategories of the ingot and mill product quality categories are available. For example, the subcategories relating to the double- or triple-melting of ingots within either the standard- or premium-quality categories are offered. As shown by the inf ormation in AMS 2380, premium-quality, double- and triple-vacuum-melted materials are called Grades 1 and 2, respectively. The same classif ication holds for double- and triple-melted ingots of standard quality. Nonpublic, company-originated purchasing specifications for ingots are issued by users for the control of composition and quality in cases where the public specif ication is not applicable.

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78 Unalloyed and Alloyed Mill Products Three sets of public specifications cover the majority of unalloyed titanium and titanium alloy mill products used in the United States. Several government agencies have prepared and are responsible for the military set (MIL-specifications), whereas nongovernment technical societies issue and maintain the other sets. The ASTM issues one and the SAE issues the other, i.e., the Aerospace Material Specifications (AMS). Tables 9 through 13 list the typical coverage of alloys and mill products afforded by the SAE, ASTM, and military specifications. Scrap No public specifications cover scrap titanium. The forms of commercial scrap that generally are recycled into titanium products through the ingot melting cycle are classified as bulk weldables (a second term is heavy bulk), light solids (e.g. , clippings from sheet), and chips and turnings. The above f arms of "prompt" scrap constitute the bulk of the titanium scrap trade that is handled by intermediate companies, the scrap dealers. They obtain this manufacturing scrap from users, segregate it by impuri ty and alloy content, and sell it to titanium ingot melters and also to the aluminum and steel industries. Only a smell amount of "obsolete" titanium scrap (e.g., worn-out engine parts) is recycled. Some of the purchasers of titanium scrap have issued private specifications that cover the quality of the products of their transactions. Other users of scrap describe the acceptable quality and limitations through purchasing agreements. A large amount of scrap that is reverted to the titanium industry through the melting cycle is "home" scrap generated by the melters and mill product produc ers . Home scrap for revert is not handled by brokers . There is an increasing trend f or the large users of titanic to sell their scrap directly back to melters instead of to brokers. Still another source of scrap titanium i s f ram f oreign users. This imported scrap usually passes through brokers for eventual use by titanium melters, if proper identification can be provided, or by other industries. A schematic scrap flow diagram is presented as Figure 11. Alloying Addition No public specifications cover the master alloy additions used In the preparation of titanium alloys. Each titanium company has purchasing specifications setting limi ts on the quality of master alloy they choose to buy. These are cited in the purchasing agreements. However, the expertise and experience of the master alloy suppliers is such that their produc ts generally exceed the quality requirements as set forth in the purchasing * Two domestic and one foreign master alloy manufacturers supply the U.S. ti tanium indust ry .

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TABLE 9 Aerospace Materials Specifications for Titanium Materials O EYE. 1l~le 4900F Plate, sheet and strip-annealed-55,000 psi yield (unalloyed Ti) 4901H Sheet, strip and plate-annealed-70,000 psi yield (unalloyed Ti) 4902C Plate' sheet and strip-annealed-40~000 psi yield (unalloyed Ti) 4905 Plate, damage tolerant grade, 6A1-4V, beta annealed 4906 Sheet and strip-6Al-4V, continuously rolled, annealed 4907C Plate, sheet, and strip-6Al-4V, extra low interstitial, annealed 4908C Sheet and strip-8Mn, annealed ~110,000 psi yield 4909C Plate, sheet, and strip-5Al-2.5Sn, extra low interstitial, annealed 4910G Plate, sheet, and str' p--5Al-2.5Sn, annealed 4911D Plate, sheet, and strip--6Al-4V, annealed 4 912A Shee t and stri p--4Al-3Mo-lV solution heat-treated 4913A Sheet and strip--4Al-3Mo-lV sol. and prec. treated 4915E Plate, sheet and strip--8Al-lMo-lV, single annealed 4916D Plate, sheet and strip--8Al-lMo-lV, duplex annealed 4917C Plate, sheet and strip--13.5V-llCr-3Al, solut~on-treated 4918E Plate, sheet and strip--6Al-6V-2Sn, annealed 4919 Sheet, strip, and plate, 6Al-2Sn-4Zr-2Mo, annealed 4921E Bars, forgings, and rings--annealed--70,000 psi yield (unalloyed Ti) 4924C Bars, forgings, and rings, 5Al-2.5Sn, extra low interstitial annealed, 90,000 psi yield 4926F Bars and rings--5A1 2. 5Sn, annealed--llO ,000 ps~ y'eld 492 8H Bars and forgings--6A1 4V, annealed--120, 000 psi yield 4930A Bars, forgings, and rings--6A1 4V, extra low interstitial, annealed 4933 Extrusions and flash-welded rings, 8Al-lMo-lV, solution heat-treated and stabilized 4934A Extrusions and flash-welded rings, 6A1-4V, solution heat-treated and aged 4 935D Ex trusions--6Al-4V annealed 493 6A Extrusions--6Al-6V-2Sn 4 941B Tu bing , welded-annealed--4 0 , 000 psi yield (unalloyed Ti) 4942B Tubing, seamless-annealed-40,000 ps! yield (unalloyed Ti) 4943A Tubing, seamless-annealed, 3A1-2.5V annealed 4944B Tubing, seamless, hydraulic, 3A1-2.5V, cold worked and stress relieved 4951D Wire, welding (unalloyed Ti) 4953A Wire, welding--5Al-2.5Sn, annealed 4954C Wire, welding--6Al-4V 4955A Wire, welding, 8Al-lMo-lV 4956A Wire, welding--6Al-4V, extra low interstitial, environment controlled 496 5D Bars ~ forgings ~ and rings--6Al-4V ~ sol e & precip. heat-treated 4966 Forgings--5Al-2 .5Sn, annealed--l1O,OOO psi yield 4967E Bars and forgings--6Al-4V, annealed, heat treatable 4970D Bars and forg~ngs, 7Al-4Mo, sol. & precip. treated 4971B Bars, forgings, and rings--6Al-6V-2Sn, annea~ ed, heat treatable

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TABLE 9 (continued) AMS No. 80 4972B Bars and rings--8Al-lMo-lV, solution treated and stabilized 497 3B Forgings--8Al-lMo-lV, solution treated and stabilized 4974 Bars and forgings--llSn-5.0Zr-2.3Al-l.OMo-0.21Si, sol. ~ precip. treated 4 975B Bars and rings--6Al-2Sn-4Zr-2Mo, sol. & precip. heat treated 4976A Forgings~6Al-2Sn-4Zr-2Mo, sol. & precip. heat-treated 4977B Bars and wire--11. 5Mo-6.0Zr-4.5Sn, solution heat-treated 4978A Bars, forgings and rings--6Al-6V-2Sn, annealed 140,000 yield 4979A Bars, forgings and rings--6Al-6V-2Sn, sol. & precip. heat-treated 4980B Bars and wire--lle5Mo-6Zr-4e5Sn, 137 5F solution heat-treated 4981A Bars and forgings--6A1-2Sn-4Zr-6Mo, sol. & precip. heat-treated 4982 Bars, 45Cb, annealed 4855 Castings, investment, 6A1-4V, annealed 49 91 Castings, investment, 6A1-4V, annealed 4995 Bi llets and Preforms, 5Al-2Sn-2Zr-4Cr-4Mo-O .1~0) premium quality powder product 4 996 Billets and preforms, 6A1-4V, premium quality, powder product 4997 Powder, 5Al-2Sn-2Zr-4Cr-4Mo-O.l(O), premium quality 4 998 Po wafer, 6A1-4V ~ premium quality Titanium and Titanium Alloys Military Handbook, MIL-HD8K-697A, June 1, 1974.

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81 TA_LE 10 AMS Materials and Product Form Correlation Plate Sheet Sttlp Tubing Extrusions Composition, Weight Percent Pure Ti, ._9 9 . 5 , ann. 40 ks i YS Pure Ti, ._99.5 , ann. 40 ksi YS Pure Ti ,~99.2, ann. 55 ksi YS Pure Ti, ~99.0, ann. 70 ksi YS Ti 0.15 to 0.20 Pd li-SAl-2.5Sn, ann. 110 ksi YS Ti-SAl-2.5Sn, LI, ann. 90 ksi Ti-(1 to 2)Ni li-2Cu Ti-2.25Al-llSn-SZr-lMo-0.2Si, STA Ti-SAl-6Sn-2Zr-lMo-0.25Si Ti-6Al-2Sn-l. SZr-lMo-0.35Bi-O. lSi li-6Al-2 Cb-lla-0.8Mo Ti-8Al-lMo-lV, single ann. Ti-8Al-lMo-IV, duplex ann. Ti-8Al-lMo-lV, sol. bested ~ stabilized li-8Mn, ann. 110 ket YS Ii-3Al-2.5 V, ann. , i-4Al-3.Io-IV, sol. treated Ti -4Al-3MO- IV, STA Ti-5Al-2Sn-2Zr-4Mo-4Cr Ti-6Al-4V, ann. 120 ksi YS Ti-6Al-4\T, cont . rolled, ann. Ti-6Al-6V, ann. heat treatable Ti-6Al-4Y, SIA li-6Al-4V, ELI, ann. Ti-6Al-69-2Sn, ann. 140 ksl YS Ti-6Al-6\'-2Sn, ann. heat treat. Ti-6Al-67-2Sn, STA Ti-6Al-2Sn-4Zr-2Mo, STA Ti-6Al-2Sn-4Zr-6Mo, STA Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.2S1 Ii- 7 Al-4Ffo, STA Ti -1A}-8V-5Fe Ti-2Al-1 lV-2Sn-ll Zr T1-3Al-8V-6Cr-4Mo-4Zr Ti-ll. SMo-6Zr-6Sn, sol. treated li-ll. SMo-6Zr-4.5Sn, }37SF sol. treated Ti-8Mo-8V-2Fe-3A1 T~-l';~-llr:r-3A1, s~1. t-~t-~4 Ti-SAl-5Sn-5Zr (NC) -i-2Cr-~Fe-~Ho (~?r) Ti-4Al-4Mn ( NC) Ti-3Al-SCr ( NC ) Ti-5.4Al-1.4Cr-1.3Fe-1.25Mo, Forging ~Bars Rlnge ~re 4951C(W) __ __ __ 49218 __ 4966D YS 4924B __ __ 4974 __ __ __ __ __ 4973A 4972A 4928G __ 4967D 4965B 4930A 4978A 4971A 4979 4975B 4981 __ 4970C __ __ __ __ 4977A __ 496UA __ __ _ __ 4968A 6968A 4923A 4923A 4925B 4925B 4927 4927 ( NC) 4969 4929 __ __ _ __ 4921B 6921B __ __ 49261) 4926D 4953(W) 4924B 4924B __ __ 4974 __ __ __ __ __ 4902B 4902B __ __ 4900D 49000 4901E 4901E __ __ 4910F 4910F 4909B 4909B 4955(W) 4915B 4915B -- 4916B 4916B 4954B(W) 4911C __ __ __ __ __ __ 4956(W) 4907B 691RC __ __ __ __ __ 4977A 4980A __ 4902B 4941 (Wd ) __ 4942(S) 4900D 4901E __ 4910F 4909B __ __ __ __ __ __ 49158 49168 4908B 4908B ~~ 4912A 4913A 4913A __ __ 4911B 4911B 4906 4906 __ __ __ __ 4907 B 4907 B 4918C 4918C __ __ __ __ __ L ~ 1 7 R L ~ 1 7 R __ __ 6943 ( S ) 4912A Note: Ann - annealed; YS - yield strength; STA - solution ant precipitation heat treated (~.e., aged); Sol - solution W - welded; S - neamles s ; NC ~ not current .

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# 82 U' o ~L# o o 4_# 0 #= Ct o o o Cat o V Cal CL U] In At: #= :> o CO ~# CO o V C) o _1 _ C: O O O Z Ca) a, to 1- ~# Cal a, to ~ 3 ~ C: Q. 00 (p~# C - t em~ ~ #-~#Cat ~ EM 1_ ~ ~# P4C' Ct L C~J ~C ~-# _4 $- ~ U. C~ ~ C~ _I t~#= 0 ~# O 0 0 ~# ~tV -~#= ~ S" ~C~ ~# _~l~ ~ ~ ~C' ', 1 1 1 C ~C ~ ~ C' e~ E ~ 3 3 3 1 1 1 1 1 1 1 1 ~1- 1 ~1 1 ~ ~O l ~I t ~O _ ~_1 _~ _~J ~-) ~u~ ~ 1- - ~O ~ 1 C~ C ~U~ ~ 1_ ~ 1 1 1 1 1 1 1 1 1 1 1 ,_ O C~ ~ ~1 _ _1 _ ~83# V #~V _ V V ~ 0 C ~0 ~V ~1 ~4 tt#t~ dV ^eJ Se CC O~ O~ ~O ^ 3 ~ ^ ~ ~ U) 3 ~# ~ ~# C ~ ~ O ~# ~ ~ ~ ~ ~ ~ C ~ ~ ~ ~ ~ 1 0 V _. ~ ~ V ~ ~J ~ ~ ~5 ~ {t ~ ~ #= C~ ~ ~ C' ~ ~ O ~ ~ O ^ - ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ C ~ ~ ~ 0 0 ~ O ~ _. O ~ 1 0 (u 64 ~ Q~ i,'d ~ Sn4 ~ ~ ~ v v O 0 1 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ #= ~ ~ ^, _~ :~ ~ v :^, ~ ~ :^ 1 1 ~ ~ ~ ~ -1 ~ Z I O O ~ C O ~ ~ OS ~ ~ ~ ~ ~ - ~ ~ _~ 3 _ ~ ~ _1 v ~o .5: ~ v ~ 3 ~ 5: _I O _1 C~ ~ ~ ~ ~ ~ O ~ ~ O 0 ~1 0 - / Ct := 1 ~ 1 ~ ~ 1 ~ 1 1 1 ~ _ ~ _~ ~ ~ ~ - ~ ~ ~ ~ _ :D ~ ~ ~ E ~ ~ ~

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83 TABLE 12 ASTM Specif ications for Titanium and Titanium Alloys . ASTM No . Specif ication Ti tie B348-7 8 B381-78 B2 65-7 9 1333 7-78 B338-78 B363-78 B36 7-7 8 F6 7-7 7 Titanium Titanium Titanium Seamless Seamless and Titanium Alloy Bars and Billets and Titanium Alloy Forgings and Titanium Alloy Strip, Sheet and Plate and Welded Titanium Pipe and Welded Titanium and Titanium Alloy Tubes for Condensers and Heat Exchanger s Seamless and Welded Unalloyed Titanium Welding Fittings Titanium and Titanium Alloy Castings Titanium for Surgical Implants TABLE 13 Military Specif ications for Titanium and Titanium Alloys Specif ication No. Title MIL-R-81588A MIL-T-134051) MIL-T-904 7G MII~-F-9 3142A MIL-T-4 6038B MI L-T-81556 MIL-T-9046H MI L-T-4 603 SA MI L-T-4 607 7A MIL-H-81200A MIL-W-6858D Rods and wire, titanium and titanium alloys Titanium powder Titanium and titanium alloy bars and forging stock Forging, titanium alloys, premium quality Titanium alloy, wrought, rods, bars and billets (for critical applications) Titanium and titanium alloys, bars, rods, and special shaped sections, extruded Titanium and titanium alloy, sheet, strip and plate Titanium alloy, high strength, wrought, (for critical applications) Titanium alloy armor plate, weldable Heat treatment of titanium and titanium alloys Welding, resistance: aluminum, magnesium, nonhardening steels or alloys, nickel alloys, heat resisting alloys and titanium alloys; spot and seam

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84 , 1 . ~ , ~_ _ . _ ~I~? ~-_ __ ~ me__ _ _. ~ ; T ~ ~ - ~D (~ `.~ t~Ei, . 1 ~ e_ ~ i_- - ~" Of DILL "~ "D ~ - ~ `~. ~ tM ____ev~l ____ ~ 1 ~ 1 ~ i#- i: ~ _ 1 1 I il 1 1 1 1 ~ I t 1 1 I r 1 1 ~. If ta~lY~! l Ia~, I 1 l~, 1 Figure 11 Titanium scrap f low diagram. 1~F l- 1 1 ~ 1 JO Source: Mineral Facts and Problems, 1975, Bureau of Mines, U.S . Department of the Interior. specifications. The titanium company specif ications include such things as the master alloy composition (e.g., 60A1-40V, 50A1-50V, 15A1-85V, 30Al-70Mo, 15Al-85Mo, and lOAl-40Cr-50V), impurity limitations, particle size range limits, and preferred packaging and marking instructions. The master alloy manufacturing facilities and operations usually are approved by end users of titanium products (e.g., the engine manufacturers).

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85 In addition to using master alloys to prepare titanium alloys, elemental additions and recycled titanium scrap (alloy) materials are used to achieve a desired titanium alloy composition. For example, Ti-6Al-4V scrap might be used to prepare Ti-3Al-2.5V alloy by dilution with appropriate amounts of unapt toyed titanium scrap or sponge. Also, in composing a charge for preparing a Ti-6Al-2Sn-4Zr-2Mo alloy, the 30Al-70Mo master alloy might be mixed with elemental additions of tin. z irconium, and make-up aluminum, as well as the sponge achieve the pref erred alloy content. Elements such as and chromium commonly are titanium base, to tin, zirconium, ~ , _ _ added to other alloys. The elemental materials may be purchased to appropriate public specifications (e.g., ASTM B-339-78 that covers tin). Miscellaneous Specifications In addition to the material speclficat~ons issued specifically for titanium products, other specs fications cover specific processes uniquely applicable to titanium alloys. For example, AMS 2631 covers the ultrasonic testing of titanium alloys, AMS 2642 and 2643 relate to the etching of titanium alloys, and AMS 2488 and 2775 deal with specific surface treatments for titanium. REFERENCES Gurevich, S. M., V. E. Blashchuk and L. M. Onoprienko, Metal Science and Heat Treatment, Vol. 15, Nos. 9-10, 1973. (Metallovedeniye i Termicheskaya Obrabotka Metallov, Moscow) . U. S. Bureau of Mines. 1976. Mineral Facts and Problems. 1975 edition, U. S . Government Printing Of f ice, Washington, D .C .

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